chore: rename closeWebPasteEvent() to cancelWebPasteEvent(), improve doc of _webPasteEventSubscription

Author: EchoEllet

lib/src/controller/quill_controller.dart

@@ -477,7 +477,7 @@ class QuillController extends ChangeNotifier {
 
     _isDisposed = true;
     if (kIsWeb) {
-      closeWebPasteEvent();
+      cancelWebPasteEvent();
     }
     super.dispose();
   }

lib/src/controller/web/quill_controller_web_real.dart

@@ -10,7 +10,8 @@ import '../quill_controller_rich_paste.dart';
 
 /// Paste event for the web.
 ///
-/// Will be `null` for non-web platforms.
+/// Will be `null` when [QuillControllerWeb.initializeWebPasteEvent] was not called
+/// or the subscription was canceled due to calling [QuillControllerWeb.cancelWebPasteEvent]
 ///
 /// See: https://developer.mozilla.org/en-US/docs/Web/API/Element/paste_event
 StreamSubscription? _webPasteEventSubscription;
@@ -30,7 +31,7 @@ extension QuillControllerWeb on QuillController {
     });
   }
 
-  void closeWebPasteEvent() {
+  void cancelWebPasteEvent() {
     _webPasteEventSubscription?.cancel();
     _webPasteEventSubscription = null;
   }

lib/src/controller/web/quill_controller_web_stub.dart

@@ -12,7 +12,7 @@ extension QuillControllerWeb on QuillController {
     );
   }
 
-  void closeWebPasteEvent() {
+  void cancelWebPasteEvent() {
     throw UnsupportedError(
       'The closeWebPasteEvent() method should be called only on web.',
     );